BHP V's Torque

JimmyCrackCorn!

End of debate is in the formula above.

Now go drive both cars and see which one suites your driving style

HashSlinging

The thing I like about driving a (Relatively powerful IMO!) diesel is the mid range, I can potter along minding my own business, see a break and really take off. While at the same time get really good MPG. There’s pro's and con's to both, but depends on your driving style. I don’t cover the same mileage as I used to and only have to visit the pumps once every two weeks now, which from a convenience point of view is handy.

brundle

JimmyCrackCorn! wrote: »

End of debate is in the formula above.

Now go drive both cars and see which one suites your driving style

and obviously the diesels are limited by the rotation speed compared to petrol alternative so much higher torque is required to put out an acceptable bhp. hence they feel 'powerful' but only for a short squirt

robbie99

JimmyCrackCorn! wrote: »

End of debate is in the formula above.

+1.

I can never understand the obsession with torque. Torque is force by distance. Give me a lever long enough and my little finger I'll generate more torque than beemer's 335d. Engine torque must be combined with the gearing ratio before it has any relevance to a car's acceleration. Power is the rate at which you can do work or something. It's a function of both torque and engine speed. As Jimmy's equation shows, BHP encompasses torque. If you want to compare things on figures alone then you should compare BHP only.

Sandwich

For those who struggle with:

BHP V's Torque


remember that its quite similar to :

Power vs. Torque

http://www.boards.ie/vbulletin/showthread.php?t=2055293659&highlight=torque

maidhc

robbie99 wrote: »

+1.

I can never understand the obsession with torque. Torque is force by distance. Give me a lever long enough and my little finger I'll generate more torque than beemer's 335d. Engine torque must be combined with the gearing ratio before it has any relevance to a car's acceleration. Power is the rate at which you can do work or something. It's a function of both torque and engine speed. As Jimmy's equation shows, BHP encompasses torque. If you want to compare things on figures alone then you should compare BHP only.

You should, assuming the engine has a CVT box which allows to always run at maximum power. Otherwise your arguments is flawed.

.

Anan1

maidhc wrote: »

You should, assuming the engine has a CVT box which allows to always run at maximum power. Otherwise your arguments is flawed.

.

Any kind of a gearbox would do the trick.

diesels do great with 6 speed gear boxes keepin the revs low
who goes around at max revs the whole time? (awaiting a hands up):D

maidhc

Anan1 wrote: »

Any kind of a gearbox would do the trick.

Not really, if you look at the old Yank tanks which had big lazy torquey v8s they often only had 2 or at most 3 speed autos.

The force (torque) of the output shaft turning is able to bring the engine from low rpm to high rpm and consequently accelerate. In a car which uses the rpm side of the equation to make up the bhp will be dead at low rpm and won't have the torque to accelerate.

This is why diesels are so good a towing, going up hills and overtaking in high gears etc, because they have brute force which equivalently powered petrols do not have.

colm_mcm

I'd actually pick the TDI over the 1.8t - sure the petrol sounds nicer, but the 130bhp engine is pretty punchy.

Anan1

maidhc wrote: »

This is why diesels are so good a towing, going up hills and overtaking in high gears etc, because they have brute force which equivalently powered petrols do not have.

...in the same gear! If you want more torque, just drop a gear or two. This is the great thing about power, it can easily be turned into torque. Unfortunately for diesels, it doesn't work the other way.

Sandwich

Anan1 wrote: »

This is the great thing about power, it can easily be turned into torque.

No.

Now we are getting muddled.

Power is the rate of doing work (Work/time). Toque is force through a distance.

You cannot turn into, or convert one to the other or visa versa.

Climate Expert

Anan1 wrote: »

...in the same gear! If you want more torque, just drop a gear or two. This is the great thing about power, it can easily be turned into torque. Unfortunately for diesels, it doesn't work the other way.

Peak torque stays the same however and peak torque will usually always be less than a diesel car.

Anan1

Sandwich wrote: »

No.

Now we are getting muddled.

Power is the rate of doing work (Work/time). Toque is force through a distance.

You cannot turn into, or convert one to the other or visa versa.

Climate Expert wrote: »

Peak torque stays the same however and peak torque will usually always be less than a diesel car.

Torque is a function of bhp and gearing. This is why a car with 150bhp but very little low-down torque can be geared to produce more torque than a turbodiesel with 140bhp and bags of low-down torque.

Climate Expert

Anan1 wrote: »

Torque is a function of bhp and gearing. This is why a car with 150bhp but very little low-down torque can be geared to produce more torque than a turbodiesel with 140bhp and bags of low-down torque.

So why don't they quote the 1.8T as having more torque than the diesel?

Anan1

Climate Expert wrote: »

So why don't they quote the 1.8T as having more torque than the diesel?

Turbodiesels tend to have higher torque peaks than petrols, but very low down. To give you an example - let's say one engine produces 1,000Nm of torque at 1,000 rpm and another produces 500Nm of torque at 2,000 rpm. They are both actually producing the same power - if you geared the second engine down by half (from 2,000 rpm to 1,000 rpm), you'd double the torque (from 500 Nm to 1,000Nm)

peasant

Anan1 wrote: »

Torque is a function of bhp and gearing. This is why a car with 150bhp but very little low-down torque can be geared to produce more torque than a turbodiesel with 140bhp and bags of low-down torque.

emmm ...that would be torque at the wheel.

The torque figures quoted in car data are taken at the crankshaft, are they not?

Anan1

peasant wrote: »

emmm ...that would be torque at the wheel.

The torque figures quoted in car data are taken at the crankshaft, are they not?

This is the point i'm making - torque at the wheel is what makes our cars go, and this can be manipulated as needed with the gearbox. As I said once before, torque is king in cars without gearboxes.;)

peasant

correct ...but for practical reasons there is only so much gearing that you can do. A 15 speed gearbox becomes somewhat undriveable

At the end of the day it is largely a question of driving style. It can be fun to wring your (petrol) cars' neck and scream around at the redline and it can be equally fun to just put the foot down from low revs and enjoy the punch in the back (brief as it is in a diesel)

maidhc

peasant wrote: »

At the end of the day it is largely a question of driving style. It can be fun to wring your (petrol) cars' neck and scream around at the redline and it can be equally fun to just put the foot down from low revs and enjoy the punch in the back (brief as it is in a diesel)

That is about the size of it.

VH

brief is the word as diesels have a tiny power band - petrol really is the enthusiasts choice

unkel

peasant wrote: »

At the end of the day it is largely a question of driving style.

That's pretty much it!

For me it is neither a small petrol engine (not even a turbo charged one) nor a turbo diesel. Best of both worlds is a (very) large NA petrol engined car. Loads of power, loads of torque and most of which available early enough in the rev range

VH

funny how people's opinions are basically a justification of what they currently own - does anyone own an engine that isn't the best?

HashSlinging

VH - unless your a le-mans driver.

Biro

VH wrote: »

funny how people's opinions are basically a justification of what they currently own - does anyone own an engine that isn't the best?

Me! I own a 4 pot turbo diesel, and I'm happy to say that I much prefer petrol!
Actually, I haven't driven many turbo petrols, but I have driven the Golf GTi Mk4. It's actually kind of diesel like in its power delivery, tails off a little earlier than I expected. Still in the power band longer than the diesel though, and feels (and is) quicker than the 130 diesel.

unkel

VH wrote: »

funny how people's opinions are basically a justification of what they currently own

You see that alot in car forums alright! I guess it is human nature to defend yourself even if you drive a sh!tty 1l petrol POS

In my case, I used to own small engined, low insurance Japanese cars just to build up no claims bonus. Once I had built up a few years NCB, I reckoned I had suffered enough and it was time for a treat. I looked at relatively high powered small petrol engined (even turbo charged) cars and drove some, but the fact I had to trash them to get performance annoyed the hell outta me.

By accident I came across a V8 petrol car (automatic!) car. I drove it and loved it. I've only had large engined V8 petrol automatic cars since!

robbie99

The title of this thread is BHP v Torque, not petrol v diesel or 2nd gear v 3rd gear.

If you want to compare cars/engines using figures then BHP is the most relevant figure. Trust me, if you have two cars of equal mass and equally well geared be it CVT, manual, auto, whatever, fuel being irrelevent, one car could be petrol and the other diesel, the car with the most BHP will accelerate quicker and reach a higher top speed regardless of which engine produces the most torque at the crankshaft. I'm amazed that people are putting such importance on the torque figure. The only people that should be interested in torque are engineers who want to calculate what stress will be put through the gearbox. When it comes to performance one engine is more powerful than the other full stop. The more powerful an engine is the quicker it can accelerate you and stronger it can push you through the air resistance. You can narrow down and say "oh, but this engine has more torque" well, you can equally say "oh, but this engine revs higher". Torque and engine speed equally contribute to making an engine more powerfull. Look at the equation.

VH

Biro wrote: »

Me! I own a 4 pot turbo diesel, and I'm happy to say that I much prefer petrol!

Ok - basically the diesel owners say diesel/torque is the best and the petrol owners say petrol/power is the best - except Biro

Mr.David

Can everyone please just make sure that their engines are spinning at 5252rpm always?

That solves this argument, cos at 5252rpm, Torque = Horsepower

peasant

robbie99 wrote: »

I'm amazed that people are putting such importance on the torque figure. The only people that should be interested in torque are engineers who want to calculate what stress will be put through the gearbox. When it comes to performance one engine is more powerful than the other full stop.

Well ...but torque does matter.

example: Saab's 2.3 turbo petrols. They have a relatively modest bhp of just over 200 ...yet they out-accelerate a 911 from 80 km/h to 120 km/h.

Yes, the 911 has the higher top speed and possibly (don't know) a better 0- 100 time too. But the mid range acceleration is what counts in real life, on actual roads with tractors and speed limits.

So don't dismiss torque completely.